carb.problem
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Elder User
Joined: Aug 2004
Posts: 620
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From: NE Wisconsin
carb.problem
Just got done with a rebuild. Badger flat tops, stock rods, Isky 256 cam, double roller timing chain set strait up, stock heads redone, weiand dual plane intake and holley 4160 600cfm. Timed to 12 deg. and no vacuum leaks. The distributor does hold a vacuum. I did go from a '78 with egr to a non egr manifold. Readjusted float bowls, set curb idle and sec idle, and the acc.pump is working. My problem is I have a huge hesitation when I snap the throttle. If I go slow to bring the rpms up everything works good. It happens off idle and at speed. Anyone have any ideas, I am out? Would the dist. make the difference?
Last edited by 2classics; Jun 1, 2005 at 09:33 PM.
Cross-Country
Joined: Oct 2001
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I've got the exact same problem right now. Fresh 400, mild cam, Holley 670 Street Avenger, Holley Street Dominator intake, mild build on the motor, stock ignition system including distributor. I also have no vacuum leaks, and my distributor also holds vacuum. I also believe that I need a bigger fuel shot when I jab on the pedal, but have played with the accelerator pump adjustment till I'm blue in the face, and no real big help. I've read about the cams, how do you change them?? I'm really interested to hear what everyone has to say about this hesitation.... 2classics, does your truck hesitate when in park and you snap it? Or just when you're in drive and you snap it??
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Joined: Apr 2005
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From: UTI student
What is it with Holleys this week. I have a 3310 750 vacum secondaries with the same problem. my carb started out only doing it while in drive. Now it seems to do it while in park but not as bad. I have a post called "problems with a rebuilt 3310" it covers my problems. I have a spring assortment for the opening rate of the secondaries. I'm wondering if maybe they need to open faster. Or maybe the secondary plates aren't properly adjusted. I have the MSD pro-billet with mechanical advance and the lightest spring installed for the advance as fast as possible. So I'm out of ideas.
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Elder User
Joined: Aug 2004
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From: NE Wisconsin
does it in park too.
Mine just has a screw holding the cam in position. It is located behind the operating lever.
Mine just has a screw holding the cam in position. It is located behind the operating lever.
Last edited by 2classics; Jun 2, 2005 at 09:36 PM.
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Elder User
Joined: Apr 2005
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From: UTI student
Great. If my problem only occured when in drive then it COULD be a secondary problem but since it happens in park then it is something else?
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Cross-Country
Joined: Oct 2001
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Actually, it won't do it in drive neither, because the secondaries won't open until the vacuum reaches a certain level, indicative of RPM's. If they are mechanical secondaries, they will not open until the pedal is pressed so far. So, if it is doing it in neutral and in drive, I would suggest that it is the accelerator pump. Try some adjustments, see where that takes you. I'm starting to think that my carb (Holley Street Avenger 670 cfm) might be a little too small for my application after adjusting my accelerator pump all I could, and am going to look at increasing the main jet a couple of sizes.....
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Elder User
Joined: Aug 2004
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From: NE Wisconsin
Update:
Adjusted some stuff last night and now it just hesitates at low rpm to WOT. Everything works good at high Rs when the main system is working. Also, sucked on the vacuum advance while snapping the throttle and it seemed to help.(maybe)
I'm going to put a lighter spring in the dist. and see if that helps.
Adjusted some stuff last night and now it just hesitates at low rpm to WOT. Everything works good at high Rs when the main system is working. Also, sucked on the vacuum advance while snapping the throttle and it seemed to help.(maybe)
I'm going to put a lighter spring in the dist. and see if that helps.